A right hander hitting a topspin serve will brush up on the ball from left to right. If you are right handed and are hitting the ball from right to left you are not hitting a topspin serve. You are hitting a 'reverse spin' serve which is sort of the equivalent of a baseball pitcher's screwball.

If you're trying to learn a topspin serve, also note the toss in the video. He's tossing the ball behind his head instead of straight up, which will force you to hit left-to-right across the ball (for a right-hander). Tossing the ball slightly behind you will also force you to arch your back and swing up through the ball.

For me, the keys to a good topspin serve are the grip and the toss... then everything else sorta falls into place.